On mobile, so sorry for the curtness.

In Asia's case, most fertile areas were already densely populated by people who shared European diseases. They were ruled by established, literate, and often extensive and/or centralized states with developed economies and comparable military and technological power (or greater with the home advantage) until rather recently. Europeans would not settle en masse in Asia when there was land easier for the taking in the Americas or otherwise and when trade with established powers in the region was simply more profitable, and they could not settle en masse in Asia without enormous opposition and the significant likelihood of defeat and loss or decline of trade. I'll remind you that the Dutch lost their holdings in Taiwan to the Chinese in the 17th century, and if Koxinga had lived a few years longer he might have defeated the Spanish in the Philippines as well. And without disease, how would millions of sedentary people be displaced or decimated to make space for a much smaller population of Europeans? Wouldn't it make more sense to exploit the large local population after their conquest?